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Basics of Case Fan Noise, Airflow, and Quieter Gaming

Read more at http://www.gamersnexus.net/guides/695-basics-of-case-fan-noise-and-airflow-quieter-gaming
Read more at http://www.gamersnexus.net/guides/692-how-many-case-fans-should-you-have

cooler master airflow
Hot and cold air are sectioned off in a top-v-bottom layout.

Cool air can be found closer to the ground since heat tends to rise, so we can take that naturally occurring phenomenon and apply it to case cooling for "free air". Here are the basics of fan placement (the bare-bones model):

1x Fan in the bottom-front of the case, near the drive bays (intake).
1x Fan in the rear-top of the case, "behind" and above the CPU (exhaust).
1x Fan in the side of the case, across from the GPU (intake).

This above setup pulls air in through the front, channels it through the drive bays (technically, this pushes hot air further into your case, but the benefit of the channeling outweighs the difference in heat), around the video card, and out the exhaust fan. The side fan forces air directly onto the hottest component (the video card), which is then swept up by the airstream produced by the front fan and escorted out of the rear exhaust fan.

If you want to take it a step further — and this is very beneficial — you could use a top-mounted fan near the rear of the case (above the CPU and core components) to get rid of that heat even faster.

It is always our recommendation that you buy cases with a minimum of 3 fans, not counting the power supply, CPU, and GPU fans.

One front-mounted intake fan.
One rear-mounted exhaust fan.
At least one other fan (intake or exhaust is fine).
One top-mounted exhaust fan.
As above, but with larger fans (140mm and 200mm preferred).
An additional, side-mounted intake fan.
An additional, bottom-mounted intake fan to pull cool air from the underside.

With the myriad of fan sizes available today it can be tough to truly understand the difference of larger fans without hands-on experience — that's what we're here for. Our previous guide explained the basics of fan placement and our recommended number of fans per system, this guide will go into depth on fan sizes, quieter gaming fans, and we'll set the stage for our next article, which will cover case fan bearing types and technologies.

fan-slider2

120mm fans used to be the prevailing option for gaming cases, but in the last year or two, companies like Cooler Master, Antec, and Thermaltake have pushed the combinatory usage of 140mm, 200mm, and even 220mm+ fans in their larger cases. 120mm fans are still abundant in the sub-$100 range, but the larger variations do have a noticeable impact on noise-levels and cooling efficiency. This is for reasons that are much more transparent than most would think — let's make it easy by looking again at the physical properties of fan size:

Larger holes allow more substance (in this case, air) to pass through them - right? The bigger the fan slot, the more air can pass through it. However, the size advantage doesn't necessarily increase the overall CFM (cubic feet per minute) of air displaced for a simple reason: larger fans spin slower, making them quieter — but they're also bigger, making them displace the same amount of air as a smaller fan with a fraction of the effort (generally increasing lifespan and decreasing fan volume). Let's compare these two sleeve bearing fans (120mm and a 200mm):
Scythe 120mm Cooler Master 200mm
CFM 110.31CFM 110CFM
RPM 1900RPM 700RPM
dBA 37dBA 19dBA

These aren't set-in-stone figures and will vary heavily based on manufacturer, operational speed, and bearing type (we'll discuss that in tomorrow's posting). That said, from the numbers above, we can see that the two fans compared in this chart are almost identical in terms of air displacement — a larger hole, arguably, may have greater access to grab a wider area of heat, but the concept is the same: each fan forces ~110 cubic feet of air per minute through the ports (which is a pretty standard amount).

The difference, as you may have noticed, comes from the RPM (revolutions per minute) of the fan blades — the higher the rotary speed, the louder the fan. Sometimes it's hard to understand exactly how loud '19 decibels' or '37 decibels' is in a real-world environment, but I'll try to break it down for you: 19dBA is my personally-imposed requirement for fans — in fact, I rarely recommend fans on our hardware forums that are louder than this setting. Speaking idiosyncratically, fans start to "annoy" me at around 27dBA (meaning I can notice the whirring noise to a point that it's more than just background sound). I've had fans that are ~47dBA in my old Antec 900 case and I could hear them in every room adjacent to mine as well as at the foot of the stairs (granted, you'd be a major creep if you knew the distance from the foot of my stairs to my room). It was annoying up to around 30ft away, which eventually led to me getting new fans. And a new case. Actually, I just got a new computer. Yeah, I know, I have to distance myself from hardware shopping websites.

If you're not sure what noise level you can tolerate, play it safe and aim for 19dBA to 25dBA fans.

Remember: bigger fans push more air through the hole, but they often spin slower, which results in the same end-result of air displacement but at a much quieter, often life-extending rate (faster fans have a tendency to heat up sleeve bearings rapidly, resulting in early death of the fans). If possible, we always recommend 140mm and 200mm fan setups; 120mm fans aren't bad, but bigger fans are definitely more friendly to the ears and streamlines heatflow.
OK... but how do I decrease case fan volume?

haf x lighting case modMy precious...Short of buying newer, quieter fans, you can go the route of controlling existing fans through the use of front-panel fan controllers (as we discussed in our 'how to soup-up your PC' article). Fan controllers are an inexpensive (and flashy) way to monitor your computer's temperatures and adjust fan levels accordingly — many of them use thermometers that can be manually placed in hot-zones of the case, and since the thermometers correspond with the local fan, singular fans can be adjusted automatically or manually for quick blasts of air to return to normal levels.

While I'm not comfortable enough with it yet to write a review, I recently added the NZXT Sentry 2 to my case (primarily for looks, if I'm honest) to control fans. It operates by plugging into the 4-pin molex power connector of each fan, then modifies the level of power supplied dependent on the monitored heat levels.

What does this mean? Well, if you have a case fan that does not have a manual adjustment, front-panel fan controllers will implement one through use of power throttling. If you're just using desktop applications and are not currently gaming, or you want to go to sleep for whatever reason, you could set the fan controller to lower fan speeds. This would diminish the power that the fans draw, which then makes them slower and decreases noise levels.

The best option to a quieter gaming PC, though, is a better understanding of fan bearing technology. Sleeve bearings are the most common and the loudest, but our next guide will explain ball bearings, fluid-dynamic systems, and rifle bearing systems.